Hi,

I just bought a 1990 XJ 4.0 liter auto. I know from the many posts here that the 4.0 head will bolt onto a 258, so an HO head should go on a non HO block just fine, right? Would I get enough power gain to make it worth while considering a can get the HO head free?

Thanks
Russ

i dont think theyre that different, i think ho difference is in fuel injection...not the actual head...

I think the intake ports are different.
http://www.pirate4x4.com/forum/showthread.php?s=&threadid=93628

The HO head is completely differemt. and that's there the whopping 13hp or whatever comes from.

have fun, it's not worth the aggravation.

I've done it a couple times. Piece of cake. I can't vouch for a power difference because both times it was on a "from-scratch" engine vs. a swap.
The non-HO intake has two holes that the head dowels key into. You'll need to elongate those holes, cut the gasket, and move the non-HO intake as high up as you can get it on the head, and also put some sealer along the top of the intake gasket just to be on the safe side. The exhaust location does not change, just the intake ports are higher.
Good luck!
Oh I used #7120's both times. 91-96 IIRC.

have any of you guys swapped on a ho head, manifold, and tb? if you ported, polished, and bored everything you could, i think you could gain 30 hp on top of a stroker....tell me what you think, i am getting ready to build a stroker and i want to max a lot of stuff out

also, i know you at least have to adapt the tps....

why dont i just start with a ho? i have a completer non ho sitting in a jeep that i have (an EXTRA one) and i think i can get the ho head and stuff for cheap, i have a friend that works at a junk yard

im stoopid, i knew this:

Cylinder head flow figures (cfm) at 25inH2O pressure drop are:

Non-HO head
Valve lift (in)..... 0.2 ... 0.3 ... 0.4 ... 0.5 ... 0.6
Intake flow.... 122.0 168.0 186.0 189.0 192.0
Exhaust flow....88.0 114.0 130.0 134.0 138.0

HO head
Valve lift (in)... 0.1 ... 0.2 ... 0.3 ... 0.4 ... 0.5 ... 0.6
Intake flow.... 66.0 128.0 179.0 206.0 209.0 209.0
Exhaust flow. 55.0 100.0 120.0 136.0 141.0 141.2

Ported HO head with 2.02/1.60 valves
Valve lift (in)... 0.1 ... 0.2 ... 0.3 ... 0.4 ... 0.5
Intake flow.... 73.9 142.4 197.8 229.8 247.0
Exhaust flow. 65.3 114.0 135.9 146.3 157.1

this is i think why non hos have more low end torque, i want a ported HO head with big valves soooo bad


a quote from yahoo stroker group:
There is no noticeable difference in the heads, except between the
Renix (87-90) and HO (91-02). There are some slight differences in the
castings, but nothing that affects performance when used stock. I think
some of the other castings have slightly thicker walls and may be better
for porting, but that's about it. One of the others who has looked into
that more can elaborate. The difference between a Renix and HO is that
the HO intake ports were raised about 1/8", making less of a turn to get
the charge (air and fuel) into the cylinder. This improved efficiency
gained 13 hp (along with minor cam and computer program changes). The
Renix head has ports that are a bit higher than the old 258 (4.2L).

Originally posted by hjeepxj
have any of you guys swapped on a ho head, manifold, and tb? if you ported, polished, and bored everything you could, i think you could gain 30 hp on top of a stroker....tell me what you think, i am getting ready to build a stroker and i want to max a lot of stuff out

Just do it ...
And while you're at it, get the cam that HESCO recommends for your particluar setup.
They've dyno'd every similar combo possable.
You will enjoy the torque the 4.2 block gives, the cam will add brute to your mid range and a cleaned up 4.0 HO head will greatly improve your top end.

Originally posted by Jaffer


Just do it ...
And while you're at it, get the cam that HESCO recommends for your particluar setup.
They've dyno'd every similar combo possable.
You will enjoy the torque the 4.2 block gives, the cam will add brute to your mid range and a cleaned up 4.0 HO head will greatly improve your top end.

sounds like i might, i just need to give a call to my buddy that works at a junk yard

btw.....im gonna use a 4.0 block, for the bigger bore, the only 258 parts im going to use is the crank and rods

Originally posted by hjeepxj



btw.....im gonna use a 4.0 block, for the bigger bore, the only 258 parts im going to use is the crank and rods

That would be how you would "stroke" a Jeep I6. It would not work the other way around (4.2L block and 4.0L crank and rods).

I would be leary of how much horsepower I made with the Jeep I6s. The blocks are really not that stout. The bottom ends are relatively small, and the head bolts are not very strong. More than one I6 block has been ruined from head bolt failure when trying to make power. They also will not handle a lot of RPM.

In stock form, they are a good engine. I just don't see spending the time and money on cams, big valves and porting.

Originally posted by Robert


That would be how you would "stroke" a Jeep I6. It would not work the other way around (4.2L block and 4.0L crank and rods).

I would be leary of how much horsepower I made with the Jeep I6s. The blocks are really not that stout. The bottom ends are relatively small, and the head bolts are not very strong. More than one I6 block has been ruined from head bolt failure when trying to make power. They also will not handle a lot of RPM.

In stock form, they are a good engine. I just don't see spending the time and money on cams, big valves and porting.

i know :cool: i am going to use arp bolts throughout

Originally posted by hjeepxj


i know :cool: i am going to use arp bolts throughout

So:question::confused:
Then you start pulling the block apart, starting with the left front corner head bolt area.:rolleyes:

Originally posted by Robert


So:question::confused:
Then you start pulling the block apart, starting with the left front corner head bolt area.:rolleyes:

how many 4.0s have YOU seen pull apart?? uh huh :rolleyes:



btw, have you ever heard of block harndener?